A right whale calf lies on its side on a Cape Lookout National Seashore beach while scientists dig around it. The other three in the group work on processing some of the samples they took from the calf./NPS

The critically endangered North Atlantic right whale population suffered a loss when a calf was either stillborn or died shortly after being born and washed ashore at Cape Lookout National Seashore in North Carolina.

The calf, with its umbilical cord still attached, was found on the beach on North Core Banks last week.

"Right whales are critically endangered and are one of the rarest marine mammals -- only a total population of about 360 animals remain in the world," park staff said on Cape Lookout's Facebook page. "Births only average 5-6 calves per year."

Laura Perry Miller, who watched as a necropsy was perfomed on the calf, said an adult right whale, apparently the calf's mother, was spotted in the ocean just off the beach.

"She blew several times about 50 yards behind the breakers, then she swam out maybe 100 yards further and sprayed a few times. I watched her for over an hour," Miller wrote on the park's Facebook page. "She seemed to be swimming in a big circle right off shore in the same spot, because right before sunset she was up closer again and I saw her barely breach.

"I talked to two ladies who stopped at the site and one of them told me she saw the mother doing the same thing yesterday," Miller added on Saturday. "The calf beached on Tuesday. That poor mama has been heartbroken out there calling for her baby for four days. Makes me sad."

Cape Lookout staff said that genetic samples from the calf might be used to "identify the mother from those that are a part of the right whale database that is maintained by the New England Aquarium."

The staff added that "that no evidence of human interaction was found during the necropsy (animal autopsy). Initial results suggest the calf died during birth, or shortly thereafter."

According to NOAA Fisheries, "By the early 1890s, commercial whalers had hunted right whales in the Atlantic to the brink of extinction. Whaling is no longer a threat, but human interactions still present the greatest danger to this species."

"Entanglement in fishing gear and vessel strikes are among the leading causes of North Atlantic right whale mortality," the agency added. "Increasing ocean noise levels from human activities interferes with whale communication, and is also a concern. ... Only 22 births have been observed in the four calving seasons since 2017, less than one-third the previous average annual birth rate for right whales."